There is a story of a Muslim prince who converted to Eastern Orthodoxy after seeing the priests performing the Liturgy of Preparation in an EO temple - he saw them slicing up an imfant rather than the Lamb. He immediately called his guards, intending to execute the priests and laity for such a heinous crime, but upon arrival saw that in fact it was merely bread and wine. Thus, he converted to the One Holy Catholic and Apostolic Faith of which the Eastern and Oriental churches are equal participants, and after refusing several entreaties from his elder beother, a higher ranking prince or bey in the Ottoman Empire to return to Islam, was executed for his apostasy, receiving the crown of martyrdom.
Thus, there is no difference between what St. Severus is saying and the prudent practices of the Eastern Orthodox. It is de rigeur in all apostolic churches to confirm the veracity of miracles; if one sees a vision, any Eastern or Oriental Orthodox who has been properly catechized will discuss it with their priest. In like manner, an Eastern Orthodox priest who experiences an apparent miracle during the Eucharist will most likely talk to his bishop; the same I expect is true of the Oriental church; I will ask Abuna in the morning. The devil routinely attacks using fake miracles and trickery, and discernment is vital. In fact my maincritique of Roman Catholicism is the degree to which they seem to embrace what is most aptly described as prelest, by credulously accepting some apparitions of the Virgin Mary in which she endorses some new doctrine, which seems to run counter to the warnings of St. Paul in Galatians, that even if an angel from Heaven comes preaching a different Gospel from that taught by the apostles, they should be anathema. In the West Syriac Rite celebrated by the most holy Syriac Orthodox Church of Antioch, which together with the Greek Orthodox Patriarchate of Antioch has established a close bond in recognition of their shared faith and in response to the terrible persecution they face together, that verse from Paul is aung as the hymn "I heard the Apostle Paul say..." before the reading of the Epistle during the Qurbono.
Thus, on this point as on any other, one cannot find any substantial or meaningful difference between Eastern and Oriental Orthodoxy. After speaking with Abuna tomorrow, God willing, I will post an update outlining what he was taught to do by his Coptic bishop when such an anomaly occurs.